1. Technical Field
The invention includes embodiments that relate to a propulsion system. The system may be used in a vehicle according to embodiments of the invention. A method related to the system and/or vehicle is provided according to embodiments of the invention.
2. Discussion of Related Art
Some vehicles may include a propulsion system that includes both a combustion engine and a battery. For a parallel-type hybrid vehicle, the vehicle power train can be driven by mechanical energy from the engine or by mechanical energy from an electric motor. The electric motor can be of relatively high voltage. The battery, however, can be of relatively lower voltage than the electric motor. The voltage differential may be addressed using a boost converter; and, a bi-directional boost converter allows the high-voltage side to communicate with the low-voltage side of the circuit. The DC-link can be on the high-voltage side of the boost converter. There may be some efficiency loss across the boost converter, and the larger the voltage differential the larger the potential loss. Further, the inclusion of diodes in the circuit may introduce potential opportunities for additional loss. It is desirable to identify, reduce and eliminate sources of efficiency loss.
Accordingly, sometimes it may be desirable to have a vehicle that differs from those vehicles that are currently available. It may be desirable to have a hybrid vehicle that has a powertrain differing from powertrains that are presently available. It may be desirable to have methods relating to a hybrid powertrain operation that differ from methods presently available.